Intraspecific divergences and phylogeography of Panzerina lanata (Lamiaceae) in Northwest China

Climactic fluctuations during the Quaternary played a crucial role in genetic diversity and population genetic structure of many plant species in northwestern China. In order to understand the impact of climate change on herbaceous plants, we studied Panzerina lanata (Lamiaceae), a widely distributed species. Two chloroplast DNA intergenic spacers (trnH-psbA and rpoB-trnC) were used to sequence 269 individuals from 27 populations and seven haplotypes were identified. Genetic structure and demographic characteristics were estimated using AMOVA, neutrality tests, and mismatch distribution analyses. The divergence times between the seven haplotypes were estimated using Beast. Our results revealed high levels of total genetic diversity (H_T = 0.673±0.0869) and low levels of average within-population genetic diversity (H_S = 0.033±0.0214). The analysis of molecular variance indicated major genetic differentiation among the three groups: northern, central, and eastern group. The species distribution modeling and demographic analysis indicated that P. lanata has not experience a recent range expansion. The divergence time within P. lanata occurred between the early Pleistocene and the late Pleistocene, which coincides with aridification and the expansion of the deserts in northwestern China that resulted in species diversification and habitat fragmentation. In addition, we speculate that the deserts and the Helan Mountains acted as effective geographic barriers that led to intraspecific diversity.